1. Field of the Invention
This invention relates to a nucleic acid, a probe and a screening method using such a probe, and more particularly to a nucleic acid, a probe comprising the nucleic acid and a screening method using the probe for a gene diagnosis.
2. Description of Related Art
As a gene mapping method of positioning a human genome on a chromosome to make a chromosomal map, there have been popularly practiced a method wherein a remaining specific human chromosome or a part of the chromosome is analyzed by using a clone panel of a somatic cell hybrid or a partially deletion chromosome between a human and a rodent, and a method wherein a cloned gene is used as a probe in a Southern blotting.
Lately, there is used a so-called in situ hybridization wherein a gene or DNA marker cloned and labeled from genome DNA is used as a probe and a molecule hybrid is directly formed in a chromosome sample on a slide glass to detect a gene existing part in order to efficiently obtain information on specified sites of many genes such as human genes and a mutual sequence order.
As the in situ hybridization, there are a method wherein DNA labeled with a radioisotope (mainly 3H) is used as a probe and its site is detected by an autoradiography, and a method wherein a fluorescence signal of a labeled DNA probe is detected by means of a fluorescence microscope.
The latter fluorescence in situ hybridization method (hereinafter referred to as FISH method) is excellent in points that an RI equipment is useless, and an operating procedure is simple, and a minute mapping is exactly carried out on a chromosome band for a short time (2 days).
At present, probes useful for various diseases/syndromes are developed for using these methods to make a clinic diagnosis. For example, there is known to be an inspection probe suitable for the FISH method on various chromosomes aimed at a syndrome having a microdeletion of a congenital anomaly syndrome. Such a probe inspects a gene of a target disease, and if an inspection result is positive (i.e. a deletion or the like is existent), the confirmed diagnosis is made.
For example, the above probe is effective for a Prader Willi syndrome because about 60% of patients have a deletion.
As mentioned above, useful probes have been found in a part of cloning of genes for the diseases. However, there are still idiopathic diseases, and inspection and diagnosis methods effective thereto are not found except for physical findings and symptoms of the disease. If a probe can be found by using a gene and/or a homolog resulted in these diseases, it becomes very beneficial in the filed of a gene diagnosis.